Question: which natural number with the highest numeric value whose instance is natural number?
Paraphrase: Which natural number with the highest numeric value has instance being also a natural number?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q21199 . ?ent wdt:P1181 ?obj . ?ent wdt:P31 wd:Q21199 } ORDER BY DESC(?obj)LIMIT 5 
Answer: 10¹²⁶ - 1, 10^123, 10^120, RSA-120, 10^117